1. Field of the Invention.
The present invention relates to a sorting device in a conveyor of plate-like workpieces, and more particularly to a sorting device within a belt conveyor situated between the output of a machine for processing successive sheets of paper or cardboard panel, and a piling station. The sorting device ejects defective sheets or panels toward a delivery area.
2. Brief Description of the Background Art.
The processing machines considered here may be machines for die-cutting blanks and /or printing of on, or more colors or metalized patterns onto the blanks and/or folding blanks into flat boxes. The potential faults requiring rejection of blanks may be, for example, color registration errors, glue stains, or inaccurate folding. These faults are detected by automatic quality control devices, based upon the scanning of photocells arranged in the travelling plane of the workpieces. The workpieces detected as being faulty are taken out of the stream of workpieces by sorting devices, also called ejectors, before the workpieces are piled into delivery batches.
A known rotating ejector rotates about a vertical axis, pivoting the sheet to be ejected between the belts of the conveyor. However, the conveyor speed and the maximum size of the sheets that can be ejected, are limited. Moreover, the rotational motion imparted to the ejected sheet may interfere with the flow of the accurate sheets, or even cause a jam.
A Linear ejector moving the ejected sheets at an angle of 45.degree. or 60.degree. to the normal stream is also known. This ejector has the advantage of not interfering with the flow of accurate sheets. However, the minimum and maximum sizes of the sheets that can be handled by this device are also limited. Also, these ejectors require accurate adjustment of the sheet thickness and are comparatively difficult to use.
Moreover, these two ejector types each require one of the conveyor belts to be raised in order to ensure an appropriate ejection. This makes the transport of the other sheets more uncertain. In addition, the ejection at high speed may be hazardous to people near the machine.
The document EP 045 713 describes a sorting device for flat folded cardboard boxes, based on mounting a lower intermediate part of the belt conveyor in a frame that is tiltable by means of a pneumatic cylinder. The frame rotates around the axis of the conveyor's rear end roller in such a way that its lowered front end roller opens an ejecting path in the downward direction for (defective boxes detected by a photocell.
U.S. Pat. No. 4,324,522 discloses a device of the same type provided for sorting metallic plates into different stacks, in which the selecting part of a tilting conveyor is the front end of a long feed conveyor. The rear end of the following conveyor may include a deflection plate which simultaneously raises with the lowering of the adjacent selecting part in order to complete the descent of the plates to be ejected.
However, this type of sorting equipment, first, uses large and heavy elements involving significant inertias, requiring powerful and hence costly drive means. Moreover, this type of sorting equipment occupies a significant volume within the machine. In addition, in the second, embodiment, a mechanism for keeping the tension in the belts of the first feed conveyor as the front end tilts should be provided.
Most important, in each of the aforementioned devices, the ejected plate-like workpieces, such cardboard boxes, are not always adequately controlled i.e. they are not held or driven along, their deflection and ejection paths. This fact may lead to situations of selective accumulation, o(r even jam, requiring machine stoppage.
The document F# 2 688 493 discloses a device for cutting out and deflecting a faulty part of a continuously processed web. This device comprises a slanted deflection plate oriented in the forward and downward direction between the vertical pairs of drive shafts of the web in normal horizontal travel. The upper edge of the plate which is located just underneath the normal path forms an anvil. A lower flap with a separation blade that is normally in raised position guides the web above the plate. When a defective web part is detected, the lower flap lowers and an upper separation flap with a blade edge rotates down against the anvil in order to cut the web and to direct it along the plate toward the ejection path, where the defective web is pulled by traction roller. At the arrival of a new adequate web part, the upper separating flap raises and the lower flap strikes the anvil so as to again cut the web and to direct the new front edge of the web in the direction of the normal travel path.
However, this processing device for a continuous web is ill-suited and too complex, hence too costly for processing successive plate-like workpieces that do not have to be cut and that preferably, must be almost continually driven by a belt conveyor or a conveyor with closely spaced parallel rollers.